Tungsten promoted catalyst for carbonylation of lower alkyl alcohols

ABSTRACT

A solid carbonylation catalyst useful for producing esters and carboxylic acids from reactants including lower alkyl alcohols and lower alkyl alcohol producing compositions in a vapor phase carbonylation process wherein the catalyst includes a catalytically effective amount of a Group VIII metal selected from platinum or palladium, and tungsten which are associated with a solid catalyst support material.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a solid catalyst andparticularly to a solid catalyst useful for producing esters andcarboxylic acids in the vapor-phase carbonylation of lower alkylalcohols, lower alkyl alcohol producing compositions, and mixturesthereof. More particularly, the present invention relates to a solidcatalyst which includes an effective amount of a Group VIII metalselected from platinum or palladium, and tungsten. The metals areassociated with a solid carrier material. The carbonylation catalyst isparticularly useful for the production of acetic acid, methyl acetateand mixtures thereof from methanol, methanol generating compounds andmixtures thereof.

[0002] Lower carboxylic acids and esters such as acetic acid and methylacetate have been known as industrial chemicals for many years. Aceticacid is used in the manufacture of a variety of intermediary andend-products. For example, an important derivative is vinyl acetatewhich can be used as monomer or co-monomer for a variety of polymers.Acetic acid itself is used as a solvent in the production ofterephthalic acid, which is widely used in the container industry, andparticularly in the formation of PET beverage containers.

[0003] There has been considerable research activity in the use of metalcatalysts for the carbonylation of lower alkyl alcohols, such asmethanol, and ethers to their corresponding carboxylic acids and esters.

[0004] Carbonylation of methanol is a well known reaction and istypically carried out in the liquid phase with a catalyst. A thoroughreview of these commercial processes and other approaches toaccomplishing the formation of acetyl from a single carbon source isdescribed by Howard et al. in Catalysis Today, 18 (1993) 325-354.Generally, the liquid phase carbonylation reaction for the preparationof acetic acid using methanol is performed using homogeneous catalystsystems comprising a Group VIII metal and iodine or an iodine-containingcompound such as hydrogen iodide and/or methyl iodide. Rhodium is themost common Group VIII metal catalyst and methyl iodide is the mostcommon promoter. These reactions are conducted in the presence of waterto prevent precipitation of the catalyst. For example, U.S. Pat. No.5,510,524 to Garland et. al. describes a liquid phase carbonylationprocess for the production of carboxylic acid by carbonylation of analkyl alcohol and/or reactive derivative by contacting the alcohol withcarbon monoxide in a liquid reaction composition which includes aniridium catalyst or rhodium catalyst, an alkyl halide, water and arhenium promoter.

[0005] A disadvantage of a homogeneous phase carbonylation process isthat additional steps are necessary for separating the products from thecatalyst solutions, and there are always handling losses of thecatalyst. Losses of the metal in the catalyst can be attributed toseveral factors, such as the plating-out of the active metal onto pipingand process equipment thereby rendering the metal inactive forcarbonylation purposes and losses due to incomplete separation of thecatalyst from the products. These losses of the metal component arecostly because the metals themselves are very expensive.

[0006] U.S. Pat. No. 5,144,068 describes the inclusion of lithium in thecatalyst system which allows the use of less water in the Rh-Ihomogeneous process. Iridium also is an active catalyst for methanolcarbonylation reactions but normally provides reaction rates lower thanthose offered by rhodium catalysts when used under otherwise similarconditions.

[0007] European Patent Application EP 0 752 406 A1 teaches thatruthenium, osmium, rhenium, zinc, cadmium, mercury, gallium, indium, ortungsten improve the rate and stability of the liquid phase Ir-Icatalyst system. Generally, the homogeneous carbonylation processespresently being used to prepare acetic acid provide relatively highproduction rates and selectivity. However, heterogeneous catalysts offerthe potential advantages of easier product separation, lower costmaterials of construction, facile recycle, and even higher rates.

[0008] Schultz, in U.S. Pat. No. 3,689,533, discloses using a supportedrhodium heterogeneous catalyst for the carbonylation of alcohols to formcarboxylic acids in a vapor phase reaction. Schultz further disclosesthe presence of a halide promoter.

[0009] Schultz in U.S. Pat. No. 3,717,670 describes a similar supportedrhodium catalyst in combination with promoters selected from Groups IB,IIIB, IVB, VB, VIB, VIII, lanthanide and actinide elements of thePeriodic Table.

[0010] Uhm, in U.S. Pat. No. 5,488,143, describes the use of alkali,alkaline earth or transition metals as promoters for supported rhodiumfor the halide-promoted, vapor phase methanol carbonylation reaction.Pimblett, in U.S. Pat. No. 5,258,549, teaches that the combination ofrhodium and nickel on a carbon support is more active than either metalby itself.

[0011] In addition to the use of iridium as a homogeneous alcoholcarbonylation catalyst, Paulik et al., in U.S. Pat. No. 3,772,380,describe the use of iridium on an inert support as a catalyst in thevapor phase, halogen-promoted, heterogeneous alcohol carbonylationprocess.

[0012] European Patent Applications EP 0 120 631 A1 and EP 0 461 802 A2describe the use of special carbons as supports for single transitionmetal component carbonylation catalysts.

[0013] European Patent Application EP 0 759 419 A1 pertains to a processfor the carbonylation of an alcohol and/or a reactive derivativethereof.

[0014] EP 0 759 419 A1 discloses a carbonylation process comprising afirst carbonylation reactor wherein an alcohol is carbonylated in theliquid phase in the presence of a homogeneous catalyst system and theoff gas from this first reactor is then mixed with additional alcoholand fed to a second reactor containing a supported catalyst. Thehomogeneous catalyst system utilized in the first reactor comprises ahalogen component and a Group VIII metal selected from rhodium andiridium. When the Group VIII metal is iridium, the homogeneous catalystsystem also may contain an optional co-promoter selected from the groupconsisting of ruthenium, osmium, rhenium, cadmium, mercury, zinc, indiumand gallium. The supported catalyst employed in the second reactorcomprises a Group VIII metal selected from the group consisting ofiridium, rhodium, and nickel, and an optional metal promoter on a carbonsupport. The optional metal promoter may be iron, nickel, lithium andcobalt. The conditions within the second carbonylation reactor zone aresuch that mixed vapor and liquid phases are present in the secondreactor. The presence of a liquid phase component in the second reactorinevitably leads to leaching of the active metals from the supportedcatalyst which, in turn, results in a substantial decrease in theactivity of the catalyst and costly replacement of the active catalystcomponent.

[0015] The literature contains several reports of the use ofrhodium-containing zeolites as vapor phase alcohol carbonylationcatalysts at one bar pressure in the presence of halide promoters. Thelead references on this type of catalyst are presented by Maneck et al.in Catalysis Today, 3 (1988), 421-429. Gelin et al., in Pure & Appl.Chem., Vol 60, No. 8, (1988) 1315-1320, provide examples of the use ofrhodium or iridium contained in zeolite as catalysts for the vapor phasecarbonylation of methanol in the presence of halide promoter. Krzywickiet al., in Journal of Molecular Catalysis, 6 (1979) 431-440, describethe use of silica, alumina, silica-alumina and titanium dioxide assupports for rhodium in the halide-promoted vapor phase carbonylation ofmethanol, but these supports are generally not as efficient as carbon.Luft et al., in U.S. Pat. No. 4,776,987 and in related disclosures,describe the use of chelating ligands chemically attached to varioussupports as a means to attach Group VIII metals to a heterogeneouscatalyst for the halide-promoted vapor phase carbonylation of ethers oresters to carboxylic anhydrides.

[0016] Evans et al., in U.S. Pat. No. 5,185,462, describe heterogeneouscatalysts for halide-promoted vapor phase methanol carbonylation basedon noble metals attached to nitrogen or phosphorus ligands attached toan oxide support.

[0017] Panster et al., in U.S. Pat. No. 4,845,163, describe the use ofrhodium-containing organopolysiloxane-ammonium compounds asheterogeneous catalysts for the halide-promoted liquid phasecarbonylation of alcohols.

[0018] Drago et al., in U.S. Pat. No. 4,417,077, describe the use ofanion exchange resins bonded to anionic forms of a single transitionmetal as catalysts for a number of carbonylation reactions including thehalide-promoted carbonylation of methanol. Although supported ligandsand anion exchange resins may be of some use for immobilizing metals inliquid phase carbonylation reactions, in general, the use of supportedligands and anion exchange resins offer no advantage in the vapor phasecarbonylation of alcohols compared to the use of the carbon as a supportfor the active metal component. Typically, these catalysts are unstableat elevated temperatures making them poorly suited to vapor phaseprocesses.

[0019] Nickel on activated carbon has been studied as a heterogeneouscatalyst for the halide-promoted vapor phase carbonylation of methanol,and increased rates are observed when hydrogen is added to the feedmixture. Relevant references to the nickel-on-carbon catalyst systemsare provided by Fujimoto et al. In Chemistry Letters (1987) 895-898 andin Journal of Catalysis, 133 (1992) 370-382 and in the referencescontained therein. Liu et al., in Ind. Eng. Chem. Res., 33 (1994)488-492, report that tin enhances the activity of the nickel-on-carboncatalyst. Mueller et al., in U.S. Pat. No. 4,918,218, disclose theaddition of palladium and optionally copper to supported nickelcatalysts for the halide-promoted carbonylation of methanol. In general,the rates of reaction provided by nickel-based catalysts are lower thanthose provided by the analogous rhodium-based catalysts when operatedunder similar conditions.

[0020] Other single metals supported on carbon have been reported byFujimoto et al. in Catalysis Letters, 2 (1989) 145-148 to have limitedactivity in the halide-promoted vapor phase carbonylation of methanol.The most active of these metals is Sn. Following Sn in order ofdecreasing activity are Pb, Mn, Mo, Cu, Cd, Cr, Re, V, Se, W, Ge and Ga.None of these other single metal catalysts are nearly as active as thosebased on Rh, Ir, Ni or the catalyst of the present invention.

[0021] A number of solid materials have been reported to catalyze thecarbonylation of methanol without the addition of the halide promoter.Gates et al., in Journal of Molecular Catalysis, 3 (1977/78) 1-9,describe a catalyst containing rhodium attached to polymer boundpolychlorinated thiophenol for the liquid phase carbonylation ofmethanol. Current, in European Patent Application EP 0 130 058 A1,describes the use of sulfided nickel containing optional molybdenum as aheterogeneous catalyst for the conversion of ethers, hydrogen and carbonmonoxide into homologous esters and alcohols.

[0022] Smith et al., in European Patent Application EP 0 596 632 A1,describe the use of mordenite zeolite containing Cu, Ni, Ir, Rh, or Coas catalysts for the halide-free carbonylation of alcohols. Feitler, inU.S. Pat. No. 4,612,387, describes the use of certain zeolitescontaining no transition metals as catalysts for the halide-freecarbonylation of alcohols and other compounds in the vapor phase.

[0023] U.S. Pat. No. 5,218,140 to Wegman describes a vapor phase processfor converting alcohols and ethers to carboxylic acids and esters by thecarbonylation of alcohols and ethers with carbon monoxide in thepresence of a metal ion exchanged heteropoly acid supported on an inertsupport. The catalyst used in the reaction includes a polyoxometalateanion in which the metal is at least one of a Group V(a) and VI(a) iscomplexed with at least one Group VIII cation such as Fe, Ru, Os, Co,Rh, Ir, Ni, Pd or Pt as catalysts for the halide-free carbonylation ofalcohols and other compounds in the vapor phase. The general formula ofa preferred form of the heteropoly acid used in the practice of theprocess is M[Q₁₂PO₄₀] where M is a Group VIII metal or a combination ofGroup VIII metals, Q is one or more of tungsten, molybdenum, vanadium,niobium, chromium, and tantalum, P is phosphorous and O is oxygen.

[0024] U.S. Pat. No. 5,900,505 to Tustin et al. describes a vapor-phasecarbonylation catalyst having iridium and at least one second metalselected from ruthenium, molybdenum, tungsten, palladium, platinum andrhenium deposited on a catalyst support material.

[0025] U.S. Pat. No. 5,414,161 to Uhm et al. describes a process for theproduction of ethanol using gas phase carbonylation of methanol. Thecatalyst used in the process includes a rhodium compound and a secondmetallic component selected from an alkali metal, alkaline earth metalor a transition metal deposited on a support material.

[0026] Accordingly, there is a need for a catalyst which can be used ina vapor phase carbonylation process for the production of carboxylicacids and their esters and in which the catalyst is maintained in thesolid phase.

SUMMARY OF THE INVENTION

[0027] Briefly, the present invention is for a solid catalyst useful forthe vapor-phase carbonylation of lower alkyl alcohols, lower alkylalcohol generating compounds, such as ether and ester derivatives of thealcohols, and mixtures thereof for producing esters and carboxylicacids. The catalyst includes a Group VIII metal selected from platinumor palladium and/or their respective metal containing compound, andtungsten and/or tungsten containing compound. The metals are associatedwith a solid carrier material which, desirably, is inert to thecarbonylation reaction. In a preferred embodiment, the catalyst furtherincludes a vaporous component comprising a halide promoter. As usedherein the term “associated with” includes any manner that permits theplatinum or palladium metal and/or a compound containing the metal, suchas a salt thereof, and the tungsten metal and/or a tungsten containingcompound to reside on or in the solid support. Non-limiting examples inwhich the metals may be associated with the solid support includeimpregnating, immersing, spraying, and coating the support sequentiallywith a solution containing the Group VIII metal and then with a tungstencontaining solution. Alternatively, the Group VIII and tungsten metalsmay be associated with the solid support by impregnating, immersing,spraying, or coating the support with a solution containing a mixture ofthe Group VIII metal and tungsten.

[0028] It is an object of the present invention to provide a catalystuseful in a vapor-phase carbonylation process. It is another object ofthe invention to provide a vapor-phase carbonylation catalyst having aGroup VIII metal selected from platinum or palladium or a compoundcontaining the respective metal and tungsten associated with a solidcarrier material. In a preferred embodiment, the catalyst includes avaporous halide promoter component.

[0029] It is another object of the invention to provide a solid phasecatalyst composition useful for vapor phase carbonylation of methanol toform acetic acid and/or methyl acetate.

[0030] These and other objects and advantages of the invention willbecome apparent to those skilled in the art from the accompanyingdetailed description.

DETAILED DESCRIPTION OF THE INVENTION

[0031] The solid supported catalyst of the present invention isparticularly useful for the continuous production of carboxylic acidsand esters by reacting lower alkyl alcohols, lower alkyl alcoholproducing compositions such as ether derivatives of the alcohols andester derivatives of the alcohols and mixtures therof in a vapor-phasecarbonylation process. The solid supported catalyst includes aneffective amount of a Group VIII metal selected from platinum orpalladium and/or a compound containing the respective metal and tungstenand/or a tungsten containing compound wherein the metals are associatedwith a solid support material. Desirably, the solid support material isinert to the carbonylation reaction. In a particularly preferredembodiment, the catalyst further includes vaporous halide promotercomponent. The catalyst is particularly useful for producing aceticacid, methyl acetate and mixtures thereof from methanol and/or amethanol generating source using heterogeneous vapor-phasecarbonylation. Desirably, the vapor-phase carbonylation process isoperated at temperatures above the dew point of the reactant and productmixtures, i.e., the temperature at which condensation occurs. However,since the dew point is a complex function of dilution (particularly withrespect to non-condensable gases such as unreacted carbon monoxide,hydrogen, or inert diluent gas), product composition, and pressure, theprocess may still be operated over a wide range of temperatures,provided the temperature exceeds the dew point of the reactants andproduct effluent. In practice, this generally dictates a temperaturerange of about 100° C. to about 500° C., with temperatures of about 100°C. to about 350° C. being preferred and temperatures of about 150° C. to275° C. being particularly useful.

[0032] As with temperature, the useful pressure range is limited by thedew point of the product mixture. Provided that the reaction is operatedat a temperature sufficient to prevent liquefaction of the reactants andproducts, a wide range of pressures may be used, e.g., pressures in therange of about 0.1 to 100 bars absolute (bara). The process preferablyis carried out at a pressure in the range of about 1 to 50 barsabsolute, most preferably, about 3 to 30 bar absolute.

[0033] Suitable feed stocks which may be carbonylated using the catalystof the present invention include lower alkyl alcohols, lower alkylalcohol producing compositions, such as ether and ester derivatives ofthe lower alkyl alcohol which generate a lower alkyl alcohol undervapor-phase carbonylation conditions, and mixtures thereof. Non-limitingexamples of feed stocks include alcohols and ethers in which analiphatic carbon atom is directly bonded to an oxygen atom of either analcoholic hydroxyl group in the compound or an ether oxygen in thecompound and may further include aromatic moieties. Preferably, the feedstock is one or more lower alkyl alcohols having from 1 to 10 carbonatoms and preferably having from 1 to 6 carbon atoms, alkane polyolshaving 2 to 6 carbon atoms, alkyl alkylene polyethers having 3 to 20carbon atoms and alkoxyalkanols having from 3 to 10 carbon atoms. Themost preferred reactant is methanol. Although methanol is the preferredfeed stock to use with the solid supported catalyst of the presentinvention and is normally fed as methanol, it can be supplied in theform of a combination of materials which generate methanol. Examples ofsuch materials include (i) methyl acetate and water and (ii) dimethylether and water. During carbonylation, both methyl acetate and dimethylether are formed within the reactor and, unless methyl acetate is thedesired product, they are recycled with water to the reactor where theyare converted to acetic acid.

[0034] The presence of water in the gaseous feed mixture is notessential when using methanol, the presence of some water is desirableto suppress formation of methyl acetate and/or dimethyl ether. Whenusing methanol to produce acetic acid, the molar ratio of water tomethanol can be 0:1 to 10:1, but preferably is in the range of 0.01:1 to1:1. When using an alternative source of methanol such as methyl acetateor dimethyl ether, the amount of water fed usually is increased toaccount for the mole of water required for hydrolysis of the methanolalternative. Accordingly, when using either methyl acetate or dimethylether, the mole ratio of water to ester or ether is in the range of 1:1to 10:1, but preferably in the range of 1:1 to 3:1. In the preparationof acetic acid, it is apparent that combinations of methanol, methylester, and/or dimethyl ether are equivalent, provided the appropriateamount of water is added to hydrolyze the ether or ester to provide themethanol reactant.

[0035] When the catalyst is used in a vapor-phase carbonylation processto produce methyl acetate, no water should be added and dimethyl etherbecomes the preferred feed stock. Further, when methanol is used as thefeed stock in the preparation of methyl acetate, it is necessary toremove water. However, the primary utility of the catalyst of thepresent invention is in the manufacture of acetic acid.

[0036] The solid supported catalyst includes a catalytically effectiveamount of platinum or palladium associated with a solid supportmaterial. The compound or form of platinum or palladium used to preparethe solid supported catalyst generally is not critical and the catalystmay be prepared from any of a wide variety of platinum or palladiumcontaining compounds. For example, platinum or palladium compounds maybe alone or contain combinations of halide, trivalent nitrogen, organiccompounds of trivalent phosphorous, carbon monoxide, hydrogen, and2,4-pentanedione. Such materials are available commercially and may beused in the preparation of the catalysts utilized in the presentinvention. In addition, the oxides of platinum or palladium may be usedif dissolved in the appropriate medium. Preferably the platinum orpalladium is a salt of one of their respective chlorides. For example,based on the availability, cost and high solubility in water a preferredplatinum or palladium is any of the various salts of hexachloroplatinate(IV) or a solution of platinum dichloride in either aqueous HCl oraqueous ammonia. Other suitable materials include platinum chloride orhexachloroplatinate complexes. One skilled in the art will understandthat use of the preferred platinum or palladium complexes should becomparable on the basis of cost, solubility, and performance.

[0037] The amount of platinum or palladium, as metal, on the support canvary from about 0.01 weight percent to about 10 weight percent, withfrom about 0.1 weight percent to about 2 weight percent platinum orpalladium being preferred based on the total weight of the solidsupported catalyst.

[0038] The solid supported catalyst also includes a predetermined amountof tungsten as a second metal component. The form of tungsten used toprepare the catalyst generally is not critical. The solid phasecomponent of the catalyst may be prepared from a wide variety oftungsten containing compounds. For example, tungsten compoundscontaining halides, a wide variety of organic (akyl and aryl)carboxylate salts, carbonyls, and alkyl or aryl groups bound totungsten, as well as various mixtures thereof, are well known, areavailable commercially, and may be used in the preparation of thecatalysts utilized in the present invention. In addition, there are avariety of tungsten oxides which may be used if dissolved in theappropriate medium. Based on its availability, cost, lower toxicity, andhigh solubility in water (the preferred solvent medium) the preferredsource of tungsten is as the ammonium tungstate.

[0039] The content of tungsten, as metal, on the support can vary over awide range, for example from about 0.01 to 10 weight percent tungstenbased on the total weight of the solid supported catalyst. However, thepreferred amount of tungsten in the catalyst is from about 0.1 to 5weight percent of tungsten based on the total weight of the solidsupported catalyst.

[0040] The solid support useful for acting as a carrier for the platinumor palladium and tungsten consists of a porous solid of such size thatit can be employed in fixed or fluidized bed reactors. The supportmaterials can have a size of from about 400 mesh per inch to about ½inch. Preferably, the support is carbon, including activated carbon,having a surface area greater than about 200 square meters/gram (m²/g).Activated carbon is well known in the art and may be derived from coalor peat having a density of from about 0.03 grams/cubic centimeter(g/cm³) to about 2.25 g/cm³. The carbon can have a surface area of fromabout 200 square meters/gram to about 1200 m²/g. Other solid supportmaterials may be used, either alone or in combination, in accordancewith the present invention include pumice, alumina, silica,silica-alumina, magnesia, diatomaceous earth, bauxite, titania,zirconia, clays, magnesium silicate, silicon carbide, zeolites, andceramics. The shape of the solid support is not particularly importantand can be regular or irregular and include extrudates, rods, balls,broken pieces and the like disposed within the reactor.

[0041] The preparation of the solid support catalyst is carried out bypreferably dissolving or dispersing the platinum or palladium andtungsten metal components in a suitable solvent. The solid supportcarrier material is then contacted with the metal containing solutions.Desirably, the Group VIII metal, i.e., platinum or palladium, andtungsten are associated with the support material as a result of solubleimpregnation of the metals which may result in either a salt of themetals, an oxide of the metals, or as a free metal deposited on thesupport. Various methods of contacting the support material with theplatinum or palladium and tungsten may be employed. For example, asolution containing the platinum or palladium can be admixed with asolution containing tungsten prior to impregnating the support material.Alternatively, the aforementioned individual solutions can beimpregnated separately into or associated with the support materialprior to impregnating the support material with the second metalcontaining solution. For example, the tungsten containing solution maybe deposited on a previously prepared catalyst support having theplatinum or palladium component already incorporated thereon. Desirably,in this alternative embodiment, the support is dried prior to contactingthe second solution. Similarly, the platinum or palladium and tungstenmay be associated with the support material in a variety of forms. Forexample, slurries of the metals can be poured over the support material,sprayed on the support material or the support material may be immersedin solutions containing excess platinum or palladium and tungsten withthe excess being subsequently removed using techniques known to thoseskilled in the art. The solvent is evaporated so that at least a portionof the platinum or palladium and tungsten is associated with the solidsupport. Drying temperatures can range from about 100° C. to about 600°C. One skilled in the art will understand that the drying time isdependent upon the temperature, humidity, and solvent. Generally, lowertemperatures require longer heating periods to effectively evaporate thesolvent from the solid support.

[0042] The liquid used to deliver the platinum or palladium and tungstenin the form a solution, dispersion, or suspension is desirably a liquidhaving a low boiling point of from about 10° C. to about 140° C.Examples of suitable solvents include carbon tetrachloride, benzene,acetone, methanol, ethanol, isopropanol, isobutanol, pentane, hexane,cyclohexane, heptane, toluene, pyridine, diethylamine, acetaldehyde,acetic acid, tetrahydrofuran and preferably, water.

[0043] In a preferred embodiment, the catalyst system further includes avaporous halide promoter selected from chlorine, bromine and iodinecompounds. Preferably, the vaporous halide is selected from bromine andiodine compounds that are vaporous under vapor-phase carbonylationconditions of temperature and pressure. Suitable halides includehydrogen halides such as hydrogen iodide and gaseous hydriodic acid;alkyl and aryl halides having up to 12 carbon atoms such as, methyliodide, ethyl iodide, 1-iodopropane, 2-iodobutane, 1-iodobutane, methylbromide, ethyl bromide, benzyl iodide and mixtures thereof. Desirably,the halide is a hydrogen halide or an alkyl halide having up to 6 carbonatoms. Non-limiting examples of preferred halides include hydrogeniodide, methyl iodide, hydrogen bromide, methyl bromide and mixturesthereof. The halide may also be a molecular halide such as I₂, Br₂, orCl₂. Preferably, the halide is introduced into the carbonylation reactorwith the reactants. As a result of contacting the active metalcomponents with the halide promoter, the ultimate active species of theplatinum or palladium and tungsten may exist as one or more coordinationcompounds or a halide thereof.

[0044] In practice, a gaseous mixture having at least one reactant of alower alkyl alcohol, and/or a lower alkyl alcohol generatingcomposition; carbon monoxide; and a halide are fed to a carbonylationreactor containing the solid supported platinum or palladium andtungsten catalyst described above. The reactant, in the vapor phase, isallowed to contact the solid supported catalyst. The reactor ismaintained under vapor-phase carbonylation conditions of temperature andpressure. If acetic acid is the desired product, the feed stock mayconsist of methyl alcohol, dimethyl ether, methyl acetate, a methylhalide or any combination thereof. If it is desired to increase theproportion of acid produced, the ester may be recycled to the reactortogether with water or introduced into a separate reactor with water toproduce the acid in a separate zone. The process includes the steps ofcontacting a gaseous mixture comprising methanol, carbon monoxide and avaporous halide promoter with the solid supported platinum or palladiumand tungsten catalyst in a carbonylation zone and recovering a gaseousproduct from the carbonylation zone.

[0045] The molar ratio of methanol or methanol equivalents to halidepresent to produce an effective carbonylation ranges from about 1:1 to10,000:1, with the preferred range being from about 5:1 to about 1000:1.

[0046] The carbon monoxide can be a purified carbon monoxide or includeother gases. The carbon monoxide need not be of a high purity and maycontain from about 1% by volume to about 99% by volume carbon monoxide,and preferably from about 70% by volume to about 99% by volume carbonmonoxide. The remainder of the gas mixture including such gases asnitrogen, hydrogen, carbon dioxide, water and paraffinic hydrocarbonshaving from one to four carbon atoms. Although hydrogen is not part ofthe reaction stoichiometry, hydrogen may be useful in maintainingoptimal catalyst activity. The preferred ratio of carbon monoxide tohydrogen generally ranges from about 99:1 to about 2:1, but ranges witheven higher hydrogen levels are also likely to be useful.

[0047] The present invention is illustrated in greater detail by thespecific examples present below. It is to be understood that theseexamples are illustrative embodiments and are not intended to belimiting of the invention, but rather are to be construed broadly withinthe scope and content of the appended claims.

[0048] In the examples which follow all of the catalysts were preparedin a similar manner except as specified otherwise.

EXAMPLES Catalyst 1

[0049] In preparing the catalyst, 579 milligrams (mg) of dihydrogenhexachioroplatinate having a Pt assay of 39.23% (1.17 mmol of Pt) wasdissolved in 30 milliliters (mL) of distilled water. This solution wasthen added to 20.0 grams of 12×40 mesh activated carbon granules(available from Calgon) contained in an evaporating dish. The activatedcarbon granules had a BET surface area in excess of 800 m²/g. Thismixture was dried using a steam bath and continuously stirred until thesupport granules became free flowing. The impregnated catalyst was thentransferred to a quartz tube measuring 106 cm long by 25 mm outerdiameter. The quartz tube was thereafter placed in a three-elementelectric tube furnace so that the mixture was located in the approximatecenter of the 61 cm long heated zone of the furnace. Nitrogen wascontinuously passed through the catalyst bed at a rate of 100 standardcubic centimeters per minute. The tube was heated from ambienttemperature to 300° C. over a 2 hour period, held at 300° C. for 2 hoursand then allowed to cool back to ambient temperature.

[0050] A second solution was prepared by dissolving 0.331 grams ofammonium tungstate (1.17 mm of W) in 30 mL of distilled water which hadbeen heated to 50° C. to allow complete dissolution of the ammoniumtungstate. This was then added to the Pt impregnated catalyst preparedabove. The catalyst was dried and transferred to a quartz tube followingthe procedure described above.

[0051] The solid supported catalyst in accordance with the presentinvention (Catalyst 1) contained 1.09% Pt, 1.03% W, and had a density of0.57 g/mL.

Catalyst Example 2

[0052] A second catalyst was prepared by dissolving 0.331 grams ofammonium tungstate (1. 17 mmol) in 30 mL of distilled water which washeated to 50° C. to allow complete dissolution of the ammoniumtungstate. This solution was then added to 20.0 grams of 12×40 meshactivated carbon granules (available from Calgon) contained in anevaporating dish. The activated carbon granules had a BET surface areain excess of 800 m²/g. The mixture was then dried and placed in a quartztube as described above in Example 1.

[0053] A second solution prepared by dissolving 0.207 grams of palladiumchloride (1. 16 mmol of Pd) in 15 mL of distilled water and 15 mL of11.6 M HCl. This was then added to the tungsten impregnated catalystprepared above. The mixture was again heated using the steam bath withcontinuous stirring until the granules became free flowing and thentransferred to a quartz tube following the procedure described above.

Comparative Catalyst Example I

[0054] In preparing a comparative catalyst containing only platinum asthe active metal, 569 mg of dihydrogen hexachloroplatinate having a Ptassay of 40% Pt (1.17 mmol of Pt) was dissolved in 30 milliliters (mL)of distilled water. This solution was added to 20.0 g of 12×40 meshactivated carbon granules contained in an evaporating dish. Theactivated carbon granules had a BET surface area in excess of 800 m²/g.This mixture was heated using a steam bath and continuously stirreduntil the support granules became free flowing. The impregnated catalystwas then transferred to a quartz tube measuring 106 cm long by 25 mmouter diameter. The quartz tube was thereafter placed in a three-elementelectric tube furnace so that the mixture was located in the approximatecenter of the 61 cm long heated zone of the furnace. Nitrogen wascontinuously passed through the catalyst bed at a rate of 100 standardcubic centimeters per minute. The tube was heated from ambienttemperature to 300° C. over a 2 hour period, held at 300° C. for 2 hoursand then allowed to cool back to ambient temperature.

[0055] The catalyst (Comparative Catalyst C-I) contained 1.10% Pt andhad a density of 0.57 g/mL.

Comparative Catalyst Example II

[0056] A second comparative catalyst (Comparative Catalyst C-II) wasprepared following the procedure of Example 1 above except that 0.206grams of ammonium molybdate (1.17 mmol) were used in place of ammoniumtungstate. The ammonium molybdate dissolved at room temperature and didnot require warming to 50° C.

Comparative Catalyst Example III

[0057] A third comparative catalyst (Comparative Catalyst C-III), wasprepared following the procedure of Example 1 above except that 0.288grams of chromium (III) acetate (1.117 mmol) were used in place ofammonium tungstate.

Comparative Catalyst Example IV

[0058] A fourth comparative catalyst (Comparative Catalyst C-IV), wasprepared following the procedure of Comparative Catalyst Example 1 aboveexcept that 290 mg of nickelous acetate tetrahydrate (1.18 mmol of Ni)was used in place of the dihydrogen hexachloroplatinate. The catalystcontained 0.34% Ni.

Comparative Catalyst Example V

[0059] A fifth comparative catalyst (Comparative Catalyst C-V), wasprepared by dissolving 0.331 grams of ammonium tungstate (1.17 mmol ofW) in 30 mL of distilled water heated to 50° C. to allow completedissolution of the ammonium tungstate. This solution was added to 20grams of Davison Silica Grade 57, (available from W. R. Grace) containedin an evaporating dish. The silica had a BET surface area of 300 m²/g.This mixture was dried using a steam bath and continuously stirred untilthe support granules became free flowing. The impregnated catalyst wasthen transferred to a quartz tube measuring 106 cm long by 25 mm outerdiameter. The quartz tube was thereafter placed in a three-elementelectric tube furnace so that the mixture was located in the approximatecenter of the 61 cm long heated zone of the furnace. Nitrogen wascontinuously passed through the catalyst bed at a rate of 100 standardcubic centimeters per minute. The tube was heated from ambienttemperature to 300° C. over a 2 hour period, held at 300° C. for 2 hoursand then allowed to cool back to ambient temperature.

[0060] A second solution was prepared by dissolving 0.579 grams ofdihydrogen hexachloroplatinate (IV) (1.16 mmol of Pt) in 30 mL ofdistilled water. This was then added to the tungsten impregnatedcatalyst above. The catalyst was dried and transferred to a quartz tubefollowing the procedure described above.

Comparative Catalyst Example VI

[0061] A sixth comparative catalyst (Comparative Catalyst C-VI) wasprepared following the procedure of Example 1 except that 20 g ofα-alumina (Engelhard α-Alumina Al-3920T) having a BET surface area of3-5 m²/g was used in place of the activated carbon.

Comparative Catalyst Example VII

[0062] A seventh comparative catalyst (Comparative Catalyst C-VII) wasprepared following the procedure of Example 2 except that 0.29 grams ofnickelous acetate tetrahydrate dissolved in 30 mL of distilled water inplace of the solution of palladium chloride in 1:1 concentratedHCl:water. The catalyst had a density of 0.57 g/mL.

Comparative Catalyst Example VIII

[0063] An eighth comparative catalyst (Comparative Catalyst C-VIII) wasprepared following the procedure of Comparative Example I above except207 mg of palladium chloride (1.17 mmol of Pd) was used in place of thedihydrogen hexachloroplatinate and an additional 10 mL of concentratedHCl was added to solubilize the palladium chloride. This procedure gavea catalyst which contained. The catalyst contained 0.61% Pd and had adensity of 0.57 g/mL.

Comparative Catalyst Example IX

[0064] A ninth comparative catalyst (Comparative Catalyst C-IX) wasprepared following the procedure of Comparative Catalyst Example I aboveexcept 418 mg iridium trichloride hydrate (1.17 mmol of Ir) of was usedin place of the dihydrogen hexachloroplatinate. The catalyst contained1.10 weight % Ir.

Carbonylation of Methanol

[0065] The reactor system consisted of a 800 to 950 mm (31.5 and 37inch) section of 6.35 mm (¼ inch) diameter tubing constructed ofHastelloy C alloy. The upper portion of the tube constituted the preheatand reaction (carbonylation) zones which were assembled by inserting aquartz wool pad 410 mm from the top of the reactor to act as support forthe catalyst, followed sequentially by (1) a 0.7 gram bed of fine quartzchips (840 microns), (2) 0.5 gram of one of the catalysts prepared asdescribed in the preceding examples, and (3) an additional 6 grams offine quartz chips. The top of the tube was attached to an inlet manifoldfor introducing liquid and gaseous feeds.

[0066] The six grams of fine quartz chips acted as a heat exchangesurface to vaporize the liquid feeds. Care was taken not to allow anyliquid feeds to contact the catalyst bed at any time, includingassembly, start-up, operation, and shutdown. The remaining lower lengthof tubing (product recovery section) consisted of a vortex cooler whichvaried in length depending on the original length of tubing employed andwas maintained at approximately 0-5° C. during operation.

[0067] The gases were fed using Brooks flow controllers and liquids werefed using a high performance liquid chromatography pump. The gaseousproducts leaving the reaction zone were condensed using a vortex cooleroperating at 0-5° C. The product reservoir was a tank placed downstreamfrom the reactor system. The pressure was maintained using a Tescom44-2300 Regulator on the outlet side of the reactor system and thetemperature of the reaction section was maintained using heating tape onthe outside of the reaction system.

[0068] Feeding of hydrogen and carbon monoxide to the reactor wascommenced while maintaining the reactor at a temperature of 240° C. anda pressure of 17.2 bara (250 psia). The flow rate of hydrogen was set at25 standard cubic cm. per minute (cc/min) and the carbon monoxide flowrate was set at 100 cc/min. The reactor section was maintained underthese conditions for 1 hour or until the temperature and pressure hadstabilized (whichever was longer.) The high pressure liquidchromatography pump was then started, feeding a mixture consisting of 70weight percent methanol and 30 weight percent methyl iodide at a rate of12 ml/min (The solution had a density of 1 g/mL.) Samples of the liquidproduct were collected and analyzed periodically using gaschromatographic techniques.

Carbonylation Example 1

[0069] The composition and weight of the samples taken periodicallyduring the procedure described above in which Catalyst 1 was used areset forth in Table 1 wherein “Time” is the total time of operation (inhours) of the carbonylation commencing with the feeding of the methanoluntil a particular sample was taken. The values set forth below “MeI”(methyl iodide), “MeOAc” (methyl acetate), “MeOH” (methanol) and “HOAc”(acetic acid) are the weight percentages of each of those compoundspresent in the sample. The weight of each sample is given in grams.TABLE I Sample Expired MeI MeOAc MeOH HOAc Sample Number Time (h) (Wt.%) (Wt. %) (Wt. %) (Wt. %) Weight(g) 1 3.5 16.11 35.79 19.73 15.46 46.22 5.5 15.99 36.48 19.89 15.37 29.8 3 8.5 16.15 36.43 19.72 15.27 30.9 410.5 17.97 31.22 30.24 6.82 29.6 5 15.5 17.8 31.34 30.27 6.8 75.6 6 18.015.85 36.19 19.59 15.19 32.9 7 23.5 15.87 35.76 19.57 15.31 70.2 8 26.517.11 33.42 25.75 9.83 29.9 9 30.5 16.63 33.22 25.73 9.93 60.9 10 35.016.86 31.09 30.59 8.06 41.5 11 39.5 18.09 31.13 29.55 8.45 80.1 12 41.518.13 31.15 29.48 8.34 28.5 13 47.5 18.09 31.14 29.5 8.39 76.5 14 49.518.5 31.82 30.35 8.62 26.2 15 51.5 18.72 31.48 29.89 8.42 23.9

[0070] The rate of acetyl production based on the preceding experimentutilizing Catalyst 1 is set forth in Table 2 below. The Sample Numberand Time values correspond to those of Table 1. “Acetyl Produced”represents the quantity, in millimoles, of methyl acetate and aceticacid produced during each increment of Time. Acetyl Produced iscalculated from the formula:

Acetyl Produced=(Sample weight (grams))×10×((weight % ofMeOAc/74)+(weight % of AcOH/60)).

[0071] “Production Rate” is the moles of Acetyl Produced per liter ofcatalyst volume per hour during each increment of Time (Time Increment),i.e., the time of operation between samples. The formula for determiningmoles of Acetyl Produced per liter of catalyst volume per hour (spacetime yield) is determined as follows:$\frac{\text{((density~~of~~the~~catalyst~~(g/ml))} \times \text{(Acetyl~~Produced))}}{\text{((grams~~of~~catalyst~~used)} \times \text{(Time~~Increment))}}$

TABLE II Sample Acetyl Rate Number Produced (mmol) (mol/L-h) 1 342.5 1122 223.2 127 3 230.8 88 4 158.5 90 5 405.9 93 6 244.2 111 7 518.4 107 8184.0 70 9 374.2 107 10 230.1 58 11 449.8 114 12 159.6 91 13 428.9 81 14150.3 86 15 135.2 77

[0072] During the 51.5 hours of testing, the catalyst produced 4.24moles of acetyl. This represents a rate 165 moles of acetyl per kilogramof catalyst per hour (acetyl/kg_(cat)-h) or, represented as a spaceyield, 94 mol of acetyl/L_(cat)-h.

Comparative Carbonylation Examples

[0073] Catalyst 2 and Comparative Catalysts C-I through C-IX were usedin the carbonylation of methanol using the same procedure and parametersas described above. The Production Rate, expressed in terms of moles ofAcetyl Produced per kilogram of catalyst per liter of catalyst volumeper hour, for each of the catalysts is shown in Table 3 below. TABLE IIICarbonylation Production Rate Example Catalyst moles/kg_(cat)-hmoles/L_(cat)-h 1 1 165 94 C-1 C-I 89 45 C-2 C-II 36 21 C-3 C-III 21 122 2 77 44 C-4 C-IV 3.0 1.7 C-5 C-V 0.9 — C-6 C-VI 0 0 C-7 C-VII 61 35C-8 C-VIII 1.7 0.8 C-9 C-IX 93 53

[0074] As can be seen from Table III, the solid supported catalysthaving platinum and tungsten on activated carbon is significantly moreactive than a catalyst derived from platinum alone. Moreover, it issurprising that promotional effect of tungsten is unique among the Group6 (Cr, Mo, W) metals.

[0075] Carbonylation example 2, when compared to comparative exampleC-IV, demonstrates that there is a substantial promotion of palladiumcatalyzed reactions upon the addition of tungsten as well.

[0076] Moreover, as can be seen from carbonylation example C-9, thecombination of platinum with tungsten is superior to comparativecatalyst C-IX wherein iridium is the active metal. Surprisingly, thecatalyst of the present invention exhibits commercially acceptablecarbonylation rates in the substantial absence of other Group VIIIcompounds and particularly compounds containing rhodium, rhenium andiridium.

[0077] Although the present invention has been shown and described interms of the presently preferred embodiment(s), it is to be understoodthat various modifications and substitutions, rearrangements of parts,components and process steps can be made by those skilled in the artwithout departing from the novel spirit and scope of the invention.

We claim:
 1. A solid carbonylation catalyst useful for producing estersand carboxylic acids from reactants including lower alkyl alcohols andlower alkyl alcohol producing compositions in a vapor phasecarbonylation process, said catalyst consisting essentially of acatalytically effective amount of a Group VIII metal selected from thegroup consisting of platinum and palladium, and tungsten and whereinsaid metals are associated with a solid catalyst support materialselected from carbon.
 2. The solid carbonylation catalyst according toclaim 1 wherein said solid support is activated carbon.
 3. The solidcarbonylation catalyst of claim 1 wherein said activated carbon has aBET surface area greater than about 800 m²/gram.
 4. The solidcarbonylation catalyst of claim 1 wherein said catalyst includes fromabout 0.1 weight percent to about 10 weight percent each of said GroupVIII metal and tungsten, wherein the weight percents of the metals isbased on the total weight of the solid supported catalyst.
 5. The solidcarbonylation catalyst of claim 1 wherein said catalyst includes fromabout 0.1 weight percent to about 2 weight percent of said Group VIIImetal and from about 0.1 to about 5 weight % of said tungsten, whereinthe weight percents of the metals is based on the total weight of thesolid supported catalyst.
 6. The solid carbonylation catalyst of claim 1wherein said Group VIII metal is platinum.
 7. The solid carbonylationcatalyst of claim 1 wherein said Group VIII metal is palladium.
 8. Thesolid carbonylation catalyst of claim 1 further comprises a halogenpromoting component selected from the group consisting of I₂, Br₂, andCl₂, hydrogen halides, gaseous hydriodic acid, alkyl and aryl halideshaving up to 12 carbon atoms, and mixtures thereof.
 9. The solidcarbonylation catalyst of claim 8 wherein said halogen promoter isselected from the group consisting of hydrogen iodide, methyl iodide,ethyl iodide, 1-iodopropane, 2-iodobutane, 1-iodobutane, hydrogenbromide, methyl bromide, ethyl bromide, benzyl iodide and mixturesthereof.
 10. The solid carbonylation catalyst of claim 1 wherein saidGroup VIII metal is selected from the group consisting of a salt ofhexachloroplatinate (IV), platinum dichloride, platinum chloride andcomplexes of hexachloroplatinate.
 11. The solid carbonylation catalystof claim 10 wherein said Group VIII metal is selected from the groupconsisting of dihydrogen hexachloroplatinate and palladium chloride. 12.A solid carbonylation catalyst useful for producing acetic acid andmethyl acetate from methanol and methanol generating compositions in avapor phase carbonylation process, said catalyst consisting essentiallyof from about 0.1 weight percent to about 10 weight percent of a GroupVIII metal selected from the group consisting of platinum and palladium,and from about 0.1 weight percent to about 10 weight percent oftungsten, wherein said metals are associated with a solid catalystsupport material selected from activated carbon, and wherein the weightpercents of the metals is based on the total weight of the solidsupported catalyst.
 13. The solid carbonylation catalyst of claim 12wherein said catalyst includes from about 0.1 weight percent to about 2weight percent of said Group VIII metal and from about 0.1 to about 5weight % tungsten.
 14. The solid carbonylation catalyst of claim 12further comprising a halogen promoting component selected from the groupconsisting of hydrogen iodide, methyl iodide, ethyl iodide,1-iodopropane, 2-iodobutane, 1-iodobutane, hydrogen bromide, methylbromide, ethyl bromide, benzyl iodide and mixtures thereof.
 15. Thesolid carbonylation catalyst of claim 14 wherein said activated carbonhas a BET surface area greater than about 800 m²/gram.
 16. The solidcarbonylation catalyst of claim 12 wherein said Group VIII metal isplatinum.
 17. The solid carbonylation catalyst of claim 12 wherein saidGroup VIII metal is palladium.
 18. A solid carbonylation catalyst usefulfor producing acetic acid and methyl acetate from methanol and methanolgenerating compositions in a vapor phase carbonylation process, saidcatalyst consisting essentially of from about 0.1 weight percent toabout 2 weight percent of Group VIII metal selected from the groupconsisting of platinum and palladium and from about 0.1 weight percentto about 5 weight percent of tungsten, wherein said metals areassociated with activated carbon as a solid catalyst support materialand wherein the weight percents of the metals is based on the totalweight of the solid supported catalyst.
 19. The solid carbonylationcatalyst of claim 18 wherein said Group VIII metal is selected from thegroup consisting of a salt of hexachloroplatinate (IV), platinumdichloride, platinum chloride and complexes of hexachloroplatinate. 20.The solid carbonylation catalyst of claim 18 wherein said Group VIIImetal is selected from the group consisting of dihydrogenhexachloroplatinate and palladium chloride.
 21. The solid carbonylationcatalyst of claim 18 further comprises a halogen promoting componentselected from the group consisting of hydrogen iodide, methyl iodide,ethyl iodide, 1-iodopropane, 2-iodobutane, 1-iodobutane, hydrogenbromide, methyl bromide, ethyl bromide, benzyl iodide and mixturesthereof.